This is because the court is concerned that people are represented by someone competent and ethical.
The court's preoccupation with whether a person is well-represented may seem absurd to someone who can't afford a lawyer and can't represent themselves; surely almost anyone would be an improvement in that case.
The problem, however, is that if a lawyer does not provide competent legal advice, the court will often intervene to prevent a miscarriage of justice. Also, the Law Society regulates lawyers to make sure they are competent and ethical, and takes disciplinary measures when they do not meet this standard.
However, no one will make sure your cousin is doing a decent (and honest) job on your behalf. If a friend or family member is incompetent, the court will not intervene, since the friend/family member is viewed as your agent, and therefore you are treated as though you are representing yourself.
This means that someone who chooses to be represented by an agent gives up the legal right to effective assistance by a lawyer. (See R v. Romanowicz, an Ontario criminal case which likely also applies to civil matters.)
That said, the court may permit someone to act as an agent so long as there is no evidence that the person is dishonest or unethical. This is a discretionary decision by a judge and so should not be considered an automatic right. In deciding whether to permit someone to act as an agent the court will consider a number of factors, including whether the proposed agent:
- Has been shown to be incompetent
- Would damage the fairness of the hearing or trial
- Is facing criminal charges involving dishonesty or the administration of justice
- Has been convicted of crimes of dishonesty
- Has otherwise demonstrated a lack of good character that would bring the administration of justice into disrepute
While it is good to be aware of the disadvantages of using an agent, the reality is that for people who can't afford a lawyer and are ineligible for pro bono legal representation, but who also face barriers to representing themselves in court (such as literacy or language skills), finding a trusted friend or family member to act as agent may be an imperfect but necessary alternative.